1. Field of the invention
This invention relates in general to formed glass manufacture, and in particular to an improved insulating glass assembly for architectural applications.
2. Description of the Prior Art
The demands of architecture often require specialty glass treatments for window, door, and wall areas. Often, these specialty requirements have been met by various assemblages of glass, as exemplified by leaded glass, glass block, and small paned windows. These assemblages have the disadvantage of multiple perimeters which increase susceptibility to air and moisture leakage and may adversely affect thermal performance. Assemblages also require higher material costs, higher initial labor costs, and higher maintenance costs, as compared to a single sheet of glass of the same area.
However, these assemblages do perform valued functions within an architectural context. Division of glazed areas into smaller units is thought to provide human scale and to increase the protective and comforting sense of enclosure. Mediating visual access, reducing glare, and creating filtered light environments are other architectural functions performed by assemblages of specialty glasses. Beveled glass, for example, is utilized for the interesting visual effects and optical distortions it provides and for its ability to bend light rays. It would be advantageous if these architectural functions could be performed by a monolithic sheet of glass.
The practice of creating an insulating glass assembly by enclosing a dead air space to act as an insulating barrier between two sheets of glass separated by a spacer is well known and widely used. The practical limits of the depth of the air space have been approximately 3/4" because when the spacer is increased to 1" or more, a natural convection pattern occurs in the larger uniform space between the two sheets of glass with the cold air tending to circulate to the bottom of the insulating assembly. This natural convection creates condensation problems and an imbalanced susceptibility to cold transfer. It would be advantageous to be able to alter this natural convection pattern and increase the volume of air space without increasing the size of the spacer used to separate the two sheets of glass. A thinner glazing configuration can translate into advantages with respect to architectural design and lower frame cost.
Additionally, because of the relatively high conductivity of glass, glazed areas depend on the surface air films on both the inside and outside of the enclosed space to provide a large portion of the resistance to heat flow. An increase of the glass surface area, and an increase, therefore, of the amount of insulating air film for a given opening would be advantageous. Increased air space has been shown to have a positive effect on reducing sound transmission levels. Surfaces of varying depth or relief may exhibit a positive effect with regard to sound reduction when compared with planar surfaces of the same material. Additionally, it has become common practice to fill the air space between two sheets of glass with a gas, or mixture of gases, such as Argon and sulfurhexafluoride, to improve the thermal conductivity and acoustical performance of the insulating glass assemblies. It would add value to the practice of gas filling if additional volume could be provided within the limits of conventional glazing configurations. Increased interior volume is also of value for the inclusion of fire retardant gels and recently developed clear, porous gels with high insulating values such as aerogel.
There is a rather substantial body of prior art relating to the broad concept of placing a sheet of glass on some sort of supporting material and softening the glass to a desired form. However, the present invention yields an accumulation of distinctive features and fulfills desired objectives not evident in prior patents.
U.S. Pat. No. 4,186,723 (Coppola et al. 1980) discloses a glass sheet arcuately contoured in the form of a plurality of sinusoidal corrugations. The sinusoidal corrugations differ in form from the present invention, and are placed in a plane that is spaced well apart from the plane of the peripheral support lip, thereby yielding a much different effect on internal convection currents than is the object of the present invention. Additionally, the extreme extension from the plane of the peripheral support flange is a limitation on the range of practical applications. Furthermore, the mold assembly method taught herein yields different optical effects and lends itself to a greater variety of forms and applications than can be derived from the disclosures of the aforementioned patent.
U.S. Pat. No. 4,210,435 teaches a method for impressing an accent line into a glass sheet. Such a procedure does not pertain to the production of an overall low relief structured glass sheet as disclosed by the present invention since the creation of functional concavities and sculptural forms is basically different from simply making an impression in the glass surface.